Method of carbonizing metal articles



T. G. SELLECK.

METHOD OF CARBONIZING METAL ARTICLES.

APPLICATION FlLED JAN. 20, 1919.

1,402A49., t t d J n. 3, 1922.

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T'. G. SELLECK.

METHOD OF CARBONIZING METAL ARTICLES. v

APLcAToN FILED JAN. 20. 1919.

Logfl& Patented Jan. 3,1922

2 SHEETS-SHEET 2.

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UlTED sTATEs TEEODORE G. sELLEcK, OF MOLINE, ILLINOIS, ASSIGNOR ro DEERE e COMPANY, OF MOLINE, ILLINOIS, A conromrov OF ILLINoIs.

METED OF CARBONIZING METAL ARTICLES.

To all whom it may camera Be it known that I, T'HEODORE Gr. SELLEK, a citizen of the United States, and a resi-;

dent of Mo1ine in the county of Rock Is-- land and State of Illincis, have invented a certain new; and Improved Method of Carbonizing Metal Articles, of which the following is a specification, reference being' had to the accompanying drawings.

`My invention has to do with the carbonization o f soft or low carbon steel for use in the manufacture of soft center steel plow shares or other articles in which it is desirable that the steel have a hard outer surface with a relatively soft hacking or center. In the manufacture of plow shares, landsides or mold-boards, for example, it 'is v necessary that the surfaces exposed to'the soil be quite hard so that they &will take a polish, will scour and will not wear ra'pidly from contact with the earth. These hard outer surfaces are, of course, b rittle and will break easily if not reinforced, and, therefore, it is desirable that the hard steel be reinforced and strengthened :by a hacking or a center layer of tough low carbon steel, and the primary object of my invention is to provide an improved process by which steel suitable for use in the manufacture of plow parts or other articles may be produced. A further object is to provide a process of carbonizing metal articles which will also have -the efl'ect of straightening them to remove waves or kinks. In describing my invention I' shall do so in connection withthe treatment of plow shares, but I wish it to be understood that my improved process may -`be applied in the treatment of a great 'variety of other articles, and the reference to' plow shares is not intended in any sense as a lmitation of the scope of the invention hereinafter claimed.

Heretofore in the carbonization of steel shares to provide them with a soft center the shares are cut from a plate or sheet of soft steel, that is to say, a plate that has a relatively low carbon content. are then placed in containers and pac-ked 'with a material that i s high in carbon, after which the containers are introduoed into a furnace where they and their contents are subjected to a high temperature for a suflicient length of time to enable the carbon to penetrate and combine with the steel adjacent to its outer surfaces. The depth to Speeification of Letters Patent.

The parts i which the carbon penetrates the metal is governed to some eXtent by the length of time the steel and the carbon material are,

` able time is required for the heat to penetrate to the center of the containers and brng the plates or other articles to the requisite high temperature. This not only lengthens the time required for the' treatment, but also increases the expense very materially. Again, the articles nearer 'the outer walls of the containers and the carbonaceous material surrounding them become hot ;before those nearer the center of the containers, and, therefore, the process begins to operate first on the articles n-earer the walls .of the containers. The result is that the latter articles absorb. more carbon than those near the center of the containers and are carbonized to a greater depth, thus preventing the production of ,a uniform product." The use of containers is also objectionable because of the added expense for containers and for the labor of preparing them for introduction into the furnace. These and other objections which might be mentioned are avoided by my invention as .will be manifest from the following description thereof.

My improved process generally stated consists in heating the articles to be car- I Patented Jan. 3, 1922.' Application filed January 20, 1919, Serial'No. 272,164.

bonized to a relatively high temperature bei 'fore subjecting them to the action of the carbonizing material, thereby insurin a uniformity of conditionduring the. su sequent treatment. After this preliminary heating, which is best done in the same heat .ing chamber where the carbonizing is effectchamber. The carbonizing gases liberated by the heat are, therefore, confined in the heating chamber, sothat more accurate regulation, and greater economy and eliciency are realizedf The mass is then subjected for the requisite period of time to a carbonizing temperature with the result that the articles are evenly and uniformly carbonized, and the whole process is accomplished in a shorter time than is thecase with the best earlier practice. The temperature at which the carbonization is e'fected is usually from 1400 to 1600' F., and the preliminary heating is p-referably from 1000 to 1300 F.,but these temperatures may be varied to a considerable extent. As in practicing my improved process no containers are employed, the cost of the containers is saved; the heating period is Shortened because there are no containers to absorb heat and interfere with the heating of the articles and the carbonaceous material; great'er economy and eficiency are obtained because the carbonizing gases are not wasted but are retained and utilized and as the articles are all of a uniform temperature when subjected to the action o-f the carbonaceous ma.- terial the result is a uniform product. While these advantages are realized even With such articles as flat plates or sheets of steel they are realized to a more marked extent in the treatment of small metal objects or irregular pieces such as gears, sleeves, bearings, tools, &c., which are apt to be injuriously afl'ected by unequal heating.

In the practice of my improved process in connection with plates used for shares, moldboards, &c., the plates are introduced into the heating chamber of a suitable furnace so that they stand. on edge and are spaced apart a suflicient distance to permit the carbonaceous material to be filled in be tween and around them and this results in the realization of a further advantage since such plates are usually more or less waved or kinky and when they are stood on edge and spaced apart and then heated to a high temperature they will straighten. This not only improves the condition of theplates themselves, but also permits the carbonaceous material to be introduced' evenly and uriformly between them so that the gases generated in the carbonizing step of the operation circulate evenly and have uniform contact with the faces of the plates and substantially the same amount of carbon will be absorbed by the plates throughout their entire face areas.

The preliminary heating not only raiscs the articles to be treated -to a uniform temperature as described, but possesses the fun,

ther advantage that it expands the metal and opens its pores, so that When the carbonaceous material is introduced and carbon gases are liberated they are not wasted,

but are immediately absorbed by the metal. The gases liberated from the carbonaceous material are produced at a lower temperature than is required to expand the metal and open its pores, and consequently where the carbonaceous material and articles are introduced into the furnace at the same time and while they are relatively cold the gases liberated before the metal reaches the temperature necessarv to effect its carbonization will be to a considerable extent lost, whereas by preliminary heating the articles and then introducing the carbonaceous material, as soon as the gases' are liberated the metal will be in a condition to absorb them, so that there will be no appreciable waste, and the carbonizing will be more quickly efected. Thus time is saved and economy of carbonaceous material is etfected as compared with the old container method in which the carbonaceous material first becomes hot and begins to yield carbon gases before the metal is prepared to absorb thecarbon, and, therefore, a surplus of carbonaceous material is required in order that there may be carbonaceous material actively generating gas at the time the metal becomes hot enough to absorb the carbon from the gas. Furthermore, by preliminary heating the articles in the heating chamber in which the subsequent step of carbonization is to be performed, they do not have to be landled while hot, and they are kept hot and in proper condition for the oontinuation of the treatment.

In the accompanying drawings I have illustrated one form of apparatus which may be advantageously empleyed in practicing my improved method, which apparatus will form the subject-matter of a sepa` rate application for patent, but it will be understood that my improved process may be practiced by the use of other forms of apparatus, as any suitable instrumentalities for practicing it may beemployed.

In the accompanying drawings,-

Fig. 1 is a longitudinal vertical section of a furnace showing a charge of lates inserted in the heating chamber, t e plates been removed and the heating chamber has been partly filled with the carbonaceous material. This figure also shows thermocouples in place for determining the temperature within the heating chamber;

Fig. 3 is a partial cross-section of the furnace, the truck and plates being shown in elevation; and i refractory material, such as fire brick, or' cement adapted to resist the effect of high temperatures, and it is provided with one or more heating chambers 5 so arranged that the hot gases of combustion do not enter said chambers but are arranged to travel around them except at the ends. The furnace has a foundation 10, side walls 11, end walls 12 and a slightly arched top 13.

Extending upwardly from the foundation 10 are transverse piers 14 upon which the heating chambers 5 are supported, and the spaces between the piers constitute fiues 15 which are in communication with the main combustion chamber 6 ofthe furnace. The fuel preferably employed for combustion is oil of a petroleum character. As has been suggested, the furnace may comprise one or more heating chambers 5, and when a series of heating chambers are provided they are separated from each other, and the furnace is so arranged as to cause the gases of combustion to flow around the heating chambers. z

Each heating chamber 5 comprises a base 16, side walls 17, a top 18 and a rear wall 19. The front of each heating chamber or compartment is provided with upper and lower doors 7-8 hinged upon the front wall of the furnace, as shown in Figs..l and 2. Between the interier side walls of the furnace and the exterior side walls' of the adjacent heating chambers at the point most remote from the combustion chamber of the furnace vertical fiues 20 are provided to form a passageway for the gases of combustion, as shown in Figs. 3 and 4, these vertical fiues being virtually a 'continuation of the fiues 15. After the gases pass through the fiues 20 they travel through the space 21 between the top of the heating chambers and the top of the furnace and thence downwardly along the sides of the heating chambers through vertical fiues 22 formed between the opposing walls of adjacent heatingchambers and vertical partitions 23 which extend down from the roof of the furnace to bases %provided between adj'acent heating chambers. Where a single heating chamber is provided one ofthe side walls of the furnace would take the place of the partition 23. The bases 24: are placed directly above the piers 14: and are spaced apart from each other so that the openings between said bases form fiues to permit hot gases to pass under the partitions 23 from one vertical flue 22 to the adjacent one, so that the gases continue to travel around the heating chambers until they pass into an evacuating stack 9 located at the combustion chamber side of the last heating chamber -of the series. This Construction is best shown in Figs. 3 and 4. Where only one heating chamber is provided the fiues formed between the bases 24 are arranged to deliver the gases directly upon the furnace' and arranged to hold said doors open for charging purposes.

27 indicates a series of plates such as are' used in the manufacture of plow shares, mold boards, &c. As illustrated in Fig. 1 these plates are introduced into the heating chambers on trucks 28 designed to be run into the heating chambers bearing a load of plates disposed on edge and spaced a distance apart. Preferably the trucks are provided with transverse rollers 28 on, which the edges of the plates rest so that after the truck has been moved into the heating chamber by holding the plates against endwise movement and pulling on the truck the latter may be withdrawn from i apart until the carbonaceous material has a been introduced, as hereinafter described, by spreaders 29 provided with'fingers which project down between adjacent plates. When a charge of plates has been introduced and the truck withdrawn the heating. chambers are closed and sealed, thermocouples 35 being introduced at the ends of the heating chambers for indicating the temperature threin. For this purpose the doors 8 are provided with openings 30 and the rear walls 'of the furnace andheating chambers are provided with openings 31 adapted to receive the thermocouples which are arranged .to project into the heating chamber so that they contact directly with the ends of one or more of'the plates therein, thus giving an accurate indication of the temperatures obtained.

32 indicates swinging doors'which are arranged to close inclined chutes or passages 34 provided in the rear walls of the furnace and heating chambers, as shown in Figs. 1 and 2, these passages being provided for the introduction into the heating chambers of carbonaceous material 33, as illustrated in Fig. 2.

Assuming that the heating chamber or chambers have been charged with the plates or other articles to be treated and that they have been closed and sealed, the hot gases resulting from combustion in the furnace pass through the fiues and spaces surroundof the process.

ing the heating chambers thereby heating said plates. This heating is continued until the plates are uniformly heated to a temperature of approximately 1200 F. which not only opens the pores of the metal for the absorption thereby of the carbon from the carbonaceous gases subsequently liberated in the heating chambers as hereafter described, but also causes the flattening of any waves or kinks in the plates. After the plates have been heated to the desired temperature the rear doors 32 are opened and a mass of carbonaceous material is introduced through the chutes 34 into the heating chambers. As the carbonaceous material enters the heating chambers an attendant working with implements such as rakes, scrapers and hook bars, introduced through the openings of the front doors '7, which have been opened, drags the carbonaceous material forward and works it down in the spaces between the plates. This is continued until the heating chambers are substantially filled and the carbonaceous material has been filled in between and around the plates, the spreaders 29, being then pulled out through the front doors. When a suh'icient quantity of carbonaceous material has been introduced to surround and cover the plates the front and rear doors are again closed and sealed and the temperature within the heating chambers is raised to the point of carbonization where it is maintained for a period of time sufficient for the plates to absorb the desired amount of carbon. The front doors 7-8 are then opened, the plates and carbon compound drawn out, and a new charge of plates introduced for a repetition It will be apparent that the process may be repeated as often as desired without allowing the furnace to cool down ,or materially reducing the temperature in the heating chambers below that required for the 'preliminary heating of the plates, so that the work may be carried on Very economically.

While in'the drawings I have shown the use of a granular carbonizing material it will be understood that my invention is not limited to the use of any particular carbonaceous material, but includes the use of any suitable material, whether powdered, granular or gaseous." Also while I prefer to use fuel oil for heating the furnace any suitable, fuel may be employed.

What I claim as my invention and desire to secure by Letters Patent, is-

1. The method of carbonizing metal articles which consists in heating the article to be carbonized by radiant heat before subjecting it to the action of carbonaceous material and afterwards heating the article to a carbonizing temperature in the presence of carbonaceous material.

2. The method of carbonizing metal articles which consists in heating the articles by radiant heat in a loose mass in the absence of carbonaceous material and then applying carbonaceous material to and around such articles and subjecting the mass to a carbonizing temperature. l

3. The method of carbonizing metal articles which consists in preliminarily heating the article by radiant heat with its surfaces to be carbonized freely exposed to the heat, and afterwards placing carbonaceous material in contact with the surfaces to be carbonized and then heating the article to introducing carbonaceous material into the heating chamber and packing it around the articles, and then heating said chamber by radiant heat to a carbonizing temperature.

6. The method of carbonizing metal articles which consists in introducing the articles into a heating chamber, subjecting the heating chamber to a temperature approximately that of the temperature of carbonization until the articles are uniformly heated, then introducing into the heating chamber and around the articles a carbonaceous material, and then subjecting the heating chamber to a higher temperature for a period .of time sufficient to cause the articles to absorb carbon from the carbonaceous material.

7. The method of carbonizing metal articles which consists in introducing the articles to be treated loosely into a suitable heating chamber closed against the admission of the products of`combustion so that they are directly exposed to the heat thereof, heating the articles in the abence of carbonaceous material, afterwardsintroducing carbonaceous material into such chamber. into direct contact with such articles, closing said chamber, and then heating the mass to a carbonizing temperature.

8. The method of carbonizing metal articles which consists in ntroducing the articles to be treated loosely into a suitable heating chamber so that they are directly exposed to the heat thereof, and heatingsuch articles in the absence of carbonizing material, afterwards packing carbonaceous material around the articles, and then heating the mass to a carbonizing temperature.

momet@ 9. The method of carbonizing metal plates which consists'in heating the plates to a relatively high temperature while standing on edge and afterwards heating the plates to a carbonizing temperature in the presence of carbonizing material.

10. The method of carbonizing metal plates which consists in standing the plates on edge in a suitable heating chamber and heating them to a relatively high temperature in the absence of carbomzing material, then introducing a carbonizing material into the heating chamber, andthen heating' the plates to a carbonizng temperature.

11. The method of carbonizin metal plates which consists in standing t e plates `on edge spaced apart from each other in plates which consists in standing the plates on edgespaced apart in a suitable heating chamber, then heating them to a relatively high temperature in the absence of carbonizing material, then introducing a solid carbonizing material into the heating chamber between and around said plates, and then heating the mass to a carbonizing temperature. v

14. The method of carbonizing metal articles which consists in placing the articles to be treated spaced apart in a heating chamber and afterwards introducing into the heating chamber and into direct association with the articles to be treated a suitable solid carbonizing material and subjecting the mass to a carbonizing temperature for a time suflicient to cause the absorption by the articles of carbon from the carbonizing material.

15. The method of carbonizing metal articles which consists in placing' the articles to be treated spaced apart in a heating chamber, heating the chamber to a high temperature in the absence of carbonizing material, and afterwards introducing into the heating chamber and into direct association with the articles to be treated' a suitable solid carbonizing material and subjecting the mass to a carbonizing temperature,

THEODORE G. sELLEcK.- 

